1. Field of the invention
The present invention relates generally to a punch retainer for use in a punch and die assembly, and more particularly to an automatic or programmable change-over ball lock punch retainer for use in a punch and die assembly.
2. Description of the Related Art
Punch retainers have been used in punch and die assemblies for many years. The punch retainers retain a punch in the die shoe while the punch is moved to form an aperture in a sheet of metal. The punch retainers are used in combination with an upper die shoe and a punch press which can hold a plurality of punches for various jobs that place apertures in a sheet of metal. A typical die shoe for multiple sheet metal parts has a plurality of punches that are not needed for each particular metal stamping process. In that case gagging retainers as known in the art have been used to place a punch in an active position for stamping of the material or to recess the punch so that punch will not form its aperture in the metal stamping process. A typical example of a die shoe having a plurality of punches includes fifteen punches that are fixed in position and form an aperture every time the stamping process is completed along with five gagging retainer punches which are liftable and capable of being deactivated into a position such that an aperture is not formed in the stamping process.
Prior art gagging retainer systems have used spring biased means to physically lift a punch away from its proper punching position or used a toggle mechanism to lower the tool holder thus making the lower punching tool inactive with respect to the work piece positioning means. However, the prior art techniques springs were not very reliable and caused down time of the stamping process and the servicing of the prior art punches required basic disassembly of the press to remove the punch and service the punch. The prior art also did not actively confirm that a punch had been placed in its retracted position.
Therefore, there is a need in the art for a punch retainer to overcome the above shortcomings.